Enlightenment

Head over to e.themes.org, and find the themes you like. Download
them, and put them in /.enlightenment/themes. Then, restart
Enlightenment (use the left-click menu). Now, you can choose your new
themes from the middle-click menu. It's really pretty simple... I
wouldn't worry about apt-getting that sort of thing (if you even can).
There is supposed to be a tool that will automatically update your
themes, but last time I checked, it was in the alpha stages. Can't
recall what it was called, sorry...